1. Field of the Invention
This invention relates to a radio communication system, more specially, gateway exchange methods for said system, and gateways, radio intelligent terminals and radio communication system applied to said method.
2. Description of the Prior Art
As Internet services such as WWW (World Wide Web) and etc. are rapidly widespread in recent years, the expansion of computer network scale and the diversity of said connecting mode are now in progress.
In order to meet said progress, the gateways which connect intelligent terminals and servers via network are required to improve the processing performance and to increase the functions.
A mobile computing is shown as an example of the diversity of connecting mode. The mobile computing is a radio communication network which is able to communicate with a computer network by using a mobile terminal network such as portable phone network adding an intelligent terminal with a radio communication function even at moving just now or even at a place impossible to connect.
FIGS. 5 and 6 are conceptual view showing the communication mode adopting the above radio communication network FIG. 5 shows a constitution of the radio communication network with public network or in-house network for example, Local Area Network (LAN).
When an user is going to execute an application in a terminal 1, the communication is performed between the terminal 1 and a sever 6 passing through a radio base station 2, a network 3, and a gateway 11 or 12. And the application is executed.
FIG. 6 shows an example of a radio communication network wherein gateways themselves have a server function, without passing through a network operated in comparatively small area such as an office, for example, shown in FIG. 5. Namely, the communication is performed between the terminal 1 and the gateway 11 or 12 via radio base station 2 and the application is to be executed.
In the radio communication network as described above, it is necessary to expand functions of gateways to meet the change of networks and to stop the operation of gateways temporarily for regular maintenance and so on. In order to continue the network operation even at the stop of the gateway, the gateway connect exchange function is required to the network, that is, a plural gateways are to be prepared as shown in FIGS. 5 and 6, and when the a gateway 11 stops, the communication is to be performed between the terminal and the server through other gateway 12.
The outline of the communication protocol between the terminal and the gateway will be explained according to FIG. 7.
An application 71 in the terminal is a program such as WWW browser that an user operates directly. And an application 75 in the gateway (shown in an example in FIG. 6 as gateway including server function) is a program for sending and receiving information with an application in the terminal, for example, a WWW server software.
A session layer protocol 72 is a protocol for offering a transfer controlling function which is common to various applications 71 and 75, for example, a means such as a transfer processing of dividing into a transferable data and of transferring per divided unit. And a management entity at management entity 73 is a program for managing system resources (such as a memory) used by a plural session processes which occurs at the data communication between a terminal and a server, and for managing processings over the whole system (for example, notice of a gateway exchange timing). A lower protocol 74 is a program and device for performing a communication control.
FIG. 8 shows the communication sequence in the communication mode.
A session layer protocol 802 in a terminal 1 is in communication 803 with a session layer protocol 804 in the gateway 11 in order to execute the application 801. At this time, an gateway exchange instruction 808 is issued by an operator to a management entity 805 in the gateway 11, and the management entity 805 sends a disconnect notice 809 to the session layer protocol 802 in the terminal 1 via the session layer protocol 804. Accordingly the session layer protocol 802 in the terminal 1 performs the disconnect display 810 to the application 801 or not, and then the execution of the application 801 is suspended.
After the gateway 11 sends out the disconnect notice 809, the gateway 11 stops according to the operator's instruction or, the function of the gateway 11. After that, the terminal 1, in order to re-execute the application 801 thus suspended, requests the session layer protocol 802 to re-connect 811 with the gateway 12 according to the information in itself.
After the session 812 is established between the session layer protocol 802 and the session layer protocol 806 in the gateway 12, the state gets to be in communication 813 and it becomes possible to re-execute the suspended application 801.
In the conventional technique as described above, however, there is a problem as follows. Namely, when the gateway connect exchange is performed because of the stop of gateway, the terminal has to finish the executing application temporarily and then re-execute the application from the beginning after re-connecting with other gateway.
And in order to re-execute the application by the the terminal after exchanging the gateway as described, it is necessary to store beforehand in the terminal the address information about a plural gateways to be changeable objects. But it means that the information necessary only for exchanging the connection of gateway are always stored in the terminal, which is equivalent to the wasteful use of resources. And this is another problem for the terminal required to be compact and have many functions.
And further problem is that, whenever it occurs that the network constitution changes by the addition, the delete and etc. of servers or gateways, the address information of the gateway stored in the terminal have to be updated. And when the connection exchanges to other gateway, it is necessary that the information such as terminal port number, terminal address and terminal capability must be negotiated between the terminal and the exchange-destination gateway. As it takes much time for the negotiation, there is a long time before the application is re-executed. This is a problem too.
And as a result of the negotiation between the terminal and the exchange-destination gateway, if said gateway does not have a capacity or resource able to accommodate the communication facility (capability) of the terminal, the terminal finishes the connection with the gateway. And the terminal tries to connect with other gateway again and again till it can find out the gateway able to accommodate the communication capability of the terminal, which is very bad in operation efficiency. But there is a possibility that these conditions will happen, and this is also a problem.
The present invention is proposed in order to solve and improve the above problems. And the object of the present invention is to provide an automatic gateway exchanging method and device wherein it is possible to exchange the connecting gateway without finishing an application executed in a terminal, it is not necessary for a terminal to always keep information of a plural gateway, it is easy for a terminal to meet various changes of network constitution, it is possible to shorten a time for the negotiation of connecting a terminal to a gateway, and it is possible to connect at a time a terminal to a gateway with a resource and capability accommodating the terminal.